Various surface treating devices of the type which includes a drive means having a rotatable output shaft with a free end upon which is mounted a rotatable element including a surface treating means are known. Well known examples of such a surface treating device are circular orbital sanders for sanding various surfaces such as metal or plastic surfaces which may be primed or painted and the like.
Such surface treating devices have been used dry, i.e., without the application of any liquid to the interface between the surface treating means and the surface being treated. Such dry operation is particularly undesirable because it creates large quantities of the airborne particulate material, causing quantities of particulate material to settle on adjacent areas and creating a potential hazard to people in the immediate area unless appropriate dust filtering devices are employed.
Wet surface treatment is also used to prevent loading or clogging of the surface treating element, e.g., coated abrasive sheet, nonwoven abrasive product, polishing pad, or the like, to reduce heat build-up, to improve the surface treatment, e.g., to impart an effect from the liquid used such as coating or polishing and for other purposes.
The benefit of wet surface treatment for rotary pad or disc applications was recognized many years ago but equipment to perform such a task was limited and inefficient. Early efforts to avoid some of the problems associated with dry surface treating and to provide wet surface treating with such devices involved first wetting the surface being treated or the surface treating means by separate external means. This provided a very brief solution of the problem since no continuous liquid supply was available. Various modifications have been made to such surface treating tools to provide a continuous source of liquid, but such modifications have increased significantly the cost of the device. Moreover, there is no known convenient means of converting unmodified devices to permit continuous wet surface treatment by supplying liquid when needed to the central portion of the surface treating pad without drastic modification of the device. One such modification, which provides a supply of liquid to the central portion of the pad or disc is the replacement of the output shaft with a hollow one to which is connected a liquid supply which is passed through the pad through a central opening. Such a modification is quite effective but it does not permit the device owner to make the modification since it requires substantial rebuilding of the device.
Examples of modified surface treating tools are shown in the following U.S. Pat. Nos.:
Bloomquist (4,102,084) disclosing a motor vehicle sanding device including a water line through the device;
Smart et al (4,129,966) disclosing a hand held grinder with water supplied from a source through a port to a sealed annular chamber surrounding the outer output shaft;
Teaque, Jr. (4,175,359) disclosing an orbital wet sander including a driving water stream which is discharged to the working surface to effect wet sanding.
Thielen (3,793,665) disclosing a floor-treating machine head assembly having openings therethrough which permit dispensing of shampoo and detergent solutions through the head assembly.
While the latter patent describes a commercially acceptable means of supplying liquid through the head assembly of the machine through openings, the liquid is not supplied to the center of the working face of the rotating pad of the machine or to the axis of rotation where it would desirably be supplied.